Downhole screw motor

ABSTRACT

To obtain technical result—creation of a new downhole screw motor ensuring a higher efficiency and increasing performance coefficient of a motor and motor operational life, improving of drilling efficiency—in a downhole screw motor comprising a stator having an internal screw surface, a rotor placed inside a stator having external screw surface, a sealing system, a spindle assembly, as per the invention as a sealing system the following system is used: a system, which contains a contact elastic, multilayered sealing agent, moreover a tough straps making layers in a sealing agent, have close ring-like shapes and are similar to the surface, to which they are fixed; the quantity of layers of a sealing agent is not more than six; in the layers separately gas and/or liquid is used as sealing media; a sealing system contains a separation joint of drilling mud flow, an electrogenerating turbine, a pumping unit for drill mud, regulating units of movement direction of sealing media and drill mud, a mud hopper, automatic control system and also, in accordance with applied sealing media, a tank-stabilizer with gas, a compressor, a heat exchanger for gas cooling and/or a tank-stabilizer with liquid, a pump, a heat exchanger for liquid cooling.

TECHNICAL FIELD

The invention relates to drilling equipment.

BACKGROUND ART

It is known a downhole screw motor comprising a body; a stator, fixedinside a body; a rotor, placed inside a stator; a spindle assembly; inthe above motor the cover (made of elastomer, for example, rubber) fixedon the stator and having an internal screw surface, is used as contactelastic sealing agent between a metal rotor and a stator. (Baldenko D.F., Baldenko F. D., Gnoyevykh A. N. Downhole screw motors: InformationManual—M.: OJSC <<Publishing Office <<Nedra>>, 1999, 375 Page).

It is known a downhole screw motor comprising a body; a stator, fixedinside a body, a rotor placed inside a stator; the quantity of screwlobes of a rotor is one less than a stator, a spindle assembly; in themotor the cover (made of elastomer, for example, rubber) applied on themetal frame of a rotor, is used as contact elastic sealing agent betweena rotor and a stator. (Patent RU No. 2011778, IPC E 21 B 4/02 dated 30Apr. 1994).

Closest analogous solution is a downhole screw motor comprising a body;a stator, fixed inside a body; a rotor, placed inside a stator; thequantity of screw lobes of a rotor is one less than a stator, a spindleassembly; in the motor the following system is used as a sealingsystem—screw cavities have been milled on the body; hollow hoses ofspecial profile are put inside above screw cavities; one end of aspecial profile hose is plugged, and other end is connected to a commonmanifold; above the hoses, inside the body a rubber stator is cured-onso that stator's screw surface is coincident with screw cavities of abody; the hose cavity through manifold and back pressure valve built ina body are filled in with oil under pressure and by that the hosesfilled by oil to a certain level, are designed for compensating for wearof a stator top. (Inventor's Certificate USSR No. 1717782 A1, IPC E 21 B4/02 dated 7 Mar. 1992).

In all of these prior arts, elastomer—rubber used for sealing purpose,has the following ineffective physical and mechanical characteristics:

For example, in comparison with steel, there is a high frictioncoefficient for the pair rubber-steel and pair rubber-rubber, lowtensile strength, low heat (Patent RU No. 2145012, IPC F 16 F 15/00dated 27 Jan. 2000; Chemical Encyclopaedical Dictionary/Head Editor I.L. Knunyants.—Moscow: Soviet Encyclopedia, 1983.—791 Pages).

Due to ineffective physical and mechanical characteristics of rubber,prior art has common disadvantages: the applied sealing agents arecharacterized by increased wear, reduced strength, reducedheat-resistant feature, not wide temperature and pressure range foroperation, impossibility of efficient control for the sealing agenttemperature to maintain a constant working temperature, impossibility toeliminate the overheating resulting in rubber destruction; the use ofrubber for the sealing of moving elements in known downhole motorsreduce the effectiveness, performance coefficient and motor operationallife, decrease drilling efficiency.

SUMMARY OF INVENTION

Technical object of the invention is creation of a new downhole screwmotor removing the above mentioned disadvantages of prior art, whichwill ensure a higher effectiveness, increasing performance coefficientof a motor and motor operational life, improving of drilling efficiency.

In order to solve this technical object in a downhole screw motorcomprising a stator having internal screw surface; a rotor havingexternal screw surface and placed inside stator, the quantity of screwlobes of a rotor is one less than of a stator; a sealing system, aspindle assembly in accordance with an invention as a sealing system thefollowing system is used: a system, which consists of a contact elastic,multilayered sealing agent rigidly connected either with a stator orwith a rotor or consists of two sealing agents, which are separatelyrigidly connected one with a stator, the other with a rotor; moreover atough straps (made of strong material, for example, metal) making layersin a sealing agent, have close ring-like shapes and are similar to thesurface, to which they are fixed; the quantity of layers of a sealingagent is not more than six; in the layers gas and/or liquid is used assealing media; a sealing system contains a separation joint of drillingmud flow, electrogenerating turbine, a pumping unit for drill mud,regulating units of movement direction of sealing media and drill mud(for example, back pressure valves), a mud hopper, automatic controlsystem (hereinafter, ACS), as well as in accordance with applied sealingmedia, tank-stabilizer with gas, a compressor, a heat exchanger for gascooling and/or tank-stabilizer with liquid, a pump, a heat exchanger forliquid cooling.

The conceptual design and function of the above mentioned contactelastic, multilayered sealing agent is described in the original source(Innovative Patent KZ No. 23655, IPC F16J 15/16 dated 17 Jan. 2012).

The concept of the invention is illustrated by schematic drawings,describing one of the best options of offered subject containing contactelastic, multilayered sealing agent rigidly connected with a stator; inthe agent in the layers gas and liquid in the order of interchange areused as sealing media. Reviewing of these schemes is enough tounderstand the concept of the invention.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a general scheme of an offered downhole screw motor.

FIG. 2 is a scheme containing a part of contact elastic, multilayeredsealing agent,

FIG. 3 and FIG. 4 are sectional elevations A and B accordingly.

MODES FOR CARRYING OUT THE INVENTION

A downhole screw motor comprises a stator 1, a rotor 2, a sealing systemcontaining a separation joint of drilling mud flow 3, a contact elastic,multilayered sealing agent 4, rigidly connected with a stator 1,moreover a tough straps 5 making layers in a sealing agent 4, have closering-like shapes and are similar to the surface, to which they arefixed, tank-stabilizer with gas 6, a compressor 7, tank-stabilizer withliquid 8, a pump 9, a heat exchanger for gas cooling 10, a heatexchanger for liquid cooling 11, an electrogenerating turbine (electricgenerator) 12, pumping unit for drill mud 13, regulating units ofmovement direction of sealing media and drill mud 14 (for example, backpressure valves), a mud hopper 15, ACS 16. (It should be noted that incase when two separate contact elastic multilayered sealing agents, oneof which rigidly connected with a stator, and the other with a rotor,are used; drill mud moves between these sealing agents). At the sametime drill mud specified as 17, sealing media: gas-18 and liquid-19 areused in a downhole screw motor.

Offered downhole screw motor operated as follows.

High pressure supplied drill mud enters a separation joint of drillingmud flow 3 and is divided into three flows. The first flow forms a mainflow of drill mud and is consumed directly for operation of a downholescrew motor providing a running torque of a rotor 2 relative to a stator1. The second flow is directed to an electrogenerating turbine 12, thethird flow—to heat exchanger for gas cooling 10 and heat exchanger forliquid cooling 11. Drill mud is a working substance of anelectrogenerating turbine 12, drill mud passing through anelectrogenerating turbine generates electric energy to power equipmentelements. Drill mud also used as cooling agent in heat exchangers 10 and11, applied in order to control temperature of sealing media of asealing system of an offered downhole screw motor. A separation joint ofdrilling mud flow 3 is managed by ACS 16, which increases or decreasesthe quantity of bleed drill mud for the operation of electrogeneratingturbine 12 depending on required horse power of appropriate consumer ofan offered device. Also under the control of ACS a separation joint ofdrilling mud flow 3, changing the quantity of drill mud delivered toheat exchangers 10 and 11, ensures the temperature control of sealingmedia (gas and liquid) in a sealing system. Managed by ACS 16tank-stabilizers 6 and 8, a compressor 7, a pump 9, heat exchangers 10and 11 regulate pressure and flow rate of sealing media (gas andliquid), increasing or decreasing permeability of clearance between astator and a rotor, in the same way allow to regulate rotational torqueof a downhole screw motor and to control drilling process, it is ofgreat importance and significantly distinguishes an offered subjectmatter from the prior art. ACS 16, besides the specified operations ofregulation and control, ensures the forcing of drill mud throughelectrogenerating turbine 12, regulating units of movement direction ofsealing media and drill mud 14 and provides the delivery of waste mud topumping unit for drill mud 13 followed by accompanied by connection withmain flow of drill mud.

Tank-stabilizer with gas 6 and tank-stabilizer with liquid 8 allowoperating relatively a compressor 7 and a pump 9 with differentefficiency, depending on the change of power on a shaft of a rotor 2 ofa downhole screw motor. Additionally the design of tank-stabilizers 6and 8 ensures the presence of initial pressure and ensures thepossibility of compensation of dynamic impulse and temperature expansionof gas and liquid during the operation and motion of a drilling systemin rock formation having a definite temperature gradient.Tank-stabilizers 6 and 8 together with a compressor 7 and a pump 9 allowcontrol a sealing system creating an opportunity to control rotationaltorque on a rotor 2 within a specified range, namely bypassing through acontact elastic, multilayered sealing agent 4 more or less of sealingmedia.

Availability of a compressor 7 and a pump 9 ensures continuous pumpingof sealing media through sealing layers 4, as well as through heatexchangers for gas and liquid 10 and 11. Sealing media (gas and liquid)heated during operation enter relatively to heat exchangers 10 and 11.Heat removal is ensured by delivery of drill mud as a cooling agent asper classical scheme for such type of equipment. Regulating units ofmovement direction of sealing media and drill mud 14 applied in thedevice prevent the back motion of drill mud and sealing media (gas andliquid), ensure the unidirectionality of motion. A mud hopper 15 ensuresthe delivery of a waste drilling mud after heat exchangers 10 and 11 andafter electrogenerating turbine 12 back to main flow of drill mud anddirects it to a pumping unit for drill mud 13. Then drill mud is sentdirectly to hollow spaces of operating chambers of a gerotor mechanism,the hollow spaces formed by a stator 1 and a rotor 2. A rotationaltorque, arising on a rotor 2, causes its eccentric motion regarding astator 1, the eccentric motion then transforms into rotating motion of ashaft of a spindle assembly (not shown in Figures.). Drill mud fromoperating chambers enters rock destruction tool and then the downhole.

Based on practical experiments concerning the development of thermalconditioning of multilayered sealing agent in order to maintain itsoperational temperature, it is reasonable to limit the quantity oflayers of a sealing agent to no more than six. The condition requiredthe quantity of layers not more than six is connected with the fact thatif the quantity of layers more than six, heat-exchange efficiencyrelated to sealing agent will increase slightly, in particular,temperature gradient will change slightly and, accordingly, the furtherincreasing of layers makes no sense.

It should be also noted that as it was mentioned above in an offeredsubject sealing media may be composed of liquid and gas phases, moreoverthe layers in sealing agent may be composed of liquid of similar ordifferent density and viscosity, and may contain or not contain thelayer with gas phase—the choice of sealing media depends on a designatedtask. One of the best options of an offered subject is above describedcase when the layers of sealing media, containing separately gas andliquid, interchange in a contact elastic, multilayered sealing agent; incase of such interchange of layers, optimum efficiency of control ofelastic and heat exchange properties of system can be reached.

1. A downhole screw motor comprising a stator having an internal screwsurface, a rotor placed inside a stator having external screw surface,the quantity of screw lobes of a rotor is one less than a stator, asealing system, a spindle assembly is different in that as a sealingsystem the following system is used: a system, which contains a contactelastic, multilayered sealing agent rigidly connected either with astator or with a rotor or contains two sealing agents, which separatelyrigidly connected one with a stator, the other with a rotor, moreover atough straps (made of strong material, for example, metal) making layersin a sealing agent, have close ring-like shapes and are similar to thesurface, to which they are fixed; the quantity of layers of a sealingagent is not more than six; in the layers separately gas and/or liquidis used as sealing media; a sealing system comprises , a separationjoint of drilling mud flow, an electrogenerating turbine, a pumping unitfor drill mud, regulating units of movement direction of sealing mediaand drill mud, a mud hopper, automatic control system and also, inaccordance with applied sealing media, a tank-stabilizer with gas, acompressor, a heat exchanger for gas cooling and/or a tank-stabilizerwith liquid, a pump, a heat exchanger for liquid cooling.